1. Field of the Invention
The present invention relates to a III-V group compound semiconductor represented by the general formula InxGayAlzN (x+y+z=1, 0xe2x89xa6xxe2x89xa61, 0xe2x89xa6yxe2x89xa61, 0xe2x89xa6zxe2x89xa61) and a light emitting device obtained by using the same.
2. Description of the Related Art
As materials of light emitting devices such as ultraviolet, blue or green light emitting diodes, ultraviolet, blue or green laser diodes and the like, III-V group compound semiconductors represented by the general formula InxGayAlzN (wherein, x+y+z=1, 0xe2x89xa6xxe2x89xa61, 0xe2x89xa6yxe2x89xa61, 0xe2x89xa6zxe2x89xa61) are known. Hereinafter, x, y and z in this general formula are described as InN crystal mixing ratio, GaN crystal mixing ratio and AlN crystal mixing ratio, in some cases. Of the III-V group compound semiconductors, those containing InN in a crystal mixing ratio of 10% or more are particularly important for display uses since it is possible to control a light emitting wavelength in the visible region, depending on InN crystal mixing ratio.
It is known, incidentally, that this compound semiconductor manifests physical properties varying significantly depending on crystal mixing ratio. For example, GaAlN-type mixed crystals containing no In can be produced under a growth temperature of 1000xc2x0 C. or more, for obtaining crystal with an excellent thermal stability. On the other hand, InGaAlN-type mixed crystals containing In are generally grown at a temperature of about 800xc2x0 C. which is relatively lower as such compound semiconductors, since thermal stability is not sufficient depending on InN crystal mixing ratio. Therefore, regarding heterojunction using an InGaAlN-type mixed crystal which is important as a light emitting device in the region of visible light, it is necessary that a layer grown directly after an active layer, what is called a barrier layer, is grown at the same level of low growth-temperature as that of the active layer. On the other hand, since a barrier layer regulates current injection into an active layer, the carrier concentration should be controlled strictly. However, it has been difficult to control the concentration of a remaining carrier in a lower range, the concentration being believed to be derived from nitrogen vacancy. Consequently, uniformity and reproducibility of light emitting efficiency were sometimes not sufficient, in the case of a light emitting device.
An object of the present invention is to provide a III-V group compound semiconductor having a concentration of a p-type dopant of 1xc3x971017 cmxe2x88x923 or more and 1xc3x971021 cmxe2x88x923 or less, which can be laminated to control the carrier concentration of an InGaAlN-type mixed crystal in a low range with high reproducibility. Another object of the present invention is to provide a III-V group compound semiconductor in which the carrier concentration of an InGaAlN-type mixed crystal is controlled in a low range with high reproducibility, and a light emitting device having high light emitting efficiency obtained by using this III-V group compound semiconductor.
The present inventors have intensively studied, in view of the above-mentioned problems, and resultantly found that an n-type III-V group compound semiconductor having a small carrier concentration can be produced with high reproducibility when a p-type dopant is doped at a specific concentration, in growth at low temperatures at which carrier concentration cannot be controlled easily, leading to completion of the invention.
Namely, the present invention relates to III-V group compound semiconductor represented by the general formula InxGayAlzN (x+y+z=1, 0xe2x89xa6xxe2x89xa61, 0yxe2x89xa61, 0xe2x89xa6zxe2x89xa61) in which the concentration of an n-type carrier is 1xc3x971019 cmxe2x88x923 or less, wherein the concentration of a p-type dopant is 1xc3x971017 cmxe2x88x923 or more and 1xc3x971021 cmxe2x88x923 or less.
Further, the present invention relates to [2] III-V group compound semiconductor having a structure in which a second layer composed of a III-V group compound semiconductor represented by the general formula InuGavAlwN (u+v+w=1, 0 less than uxe2x89xa61, 0xe2x89xa6vxe2x89xa61, 0xe2x89xa6w less than 1) is adjacent to a first layer composed of a III-V group compound semiconductor represented by the general formula InxGayAlzN (x+y+z=1, 0xe2x89xa6xxe2x89xa6=1, 0xe2x89xa6yxe2x89xa61, 0xe2x89xa6zxe2x89xa61) in which the concentration of an n-type carrier is 1xc3x971019 cmxe2x88x923 or less, wherein the concentration of a p-type dopant is 1xc3x971017 cmxe2x88x923 or more and 1xc3x971021 cmxe2x88x923 or less, and the band gap is larger than that of the above-mentioned second layer.
Further, the present invention relates to [3] a III-V group compound semiconductor having a structure in which a layer composed of a III-V group compound semiconductor represented by the general formula InxGayAlzN (x+y+z=1, 0xe2x89xa6xxe2x89xa61, 0xe2x89xa6yxe2x89xa61, 0xe2x89xa6zxe2x89xa61) in which the concentration of an n-type carrier is 1xc3x971019 cmxe2x88x923 or less, wherein the concentration of a p-type dopant is 1xc3x971017 cmxe2x88x923 or more and 1xc3x971021 cmxe2x88x923 or less is adjacent to a layer composed of a p-type III-V group compound semiconductor represented by the general formula InaGabAlcN (a+b+c=1, 0xe2x89xa6axe2x89xa61, 0xe2x89xa6bxe2x89xa61, 0xe2x89xa6cxe2x89xa61).
Further, the present invention relates to [4] a III-V group compound semiconductor having a structure comprising at least one layer composed of a III-V group compound semiconductor represented by the general formula InxGayAlzN (x+y+z=1, 0xe2x89xa6xxe2x89xa61, 0xe2x89xa6yxe2x89xa61, 0xe2x89xa6zxe2x89xa61) in which the concentration of an n-type carrier is 1xc3x971019 cmxe2x88x923 or less, wherein the concentration of a p-type dopant is 1xc3x971017 cmxe2x88x923 or more and 1xc3x971021 cmxe2x88x923 or less, between a layer composed of a III-V group compound semiconductor represented by the general formula InuGavAlwN (u+v+w=1, 0 less than uxe2x89xa61, 0xe2x89xa6v less than 1, 0xe2x89xa6w less than 1) and a layer composed of a p-type III-V group compound semiconductor represented by the general formula InaGabAlcN (a+b+c=1, 0xe2x89xa6axe2x89xa61, 0xe2x89xa6bxe2x89xa61, 0xe2x89xa6cxe2x89xa61).
Further, the present invention relates to [5] a III-V group compound semiconductor having a structure comprising a second layer composed of a III-V group compound semiconductor represented by the general formula InuGavAlwN (u+v+w=1, 0 less than uxe2x89xa61, 0xe2x89xa6v less than 1, 0xe2x89xa6w less than 1) carrying thereon a laminated layer composed of an n-type III-V group compound semiconductor represented by the general formula InpGaqAlrN (p+q+r=1, 0xe2x89xa6pxe2x89xa61, 0xe2x89xa6qxe2x89xa61, 0xe2x89xa6rxe2x89xa61) having larger band gap than that of the above-mentioned second layer, and at least one layer composed of a III-V group compound semiconductor represented by the general formula InxGayAlzN (x+y+z=1, 0xe2x89xa6xxe2x89xa61, 0xe2x89xa6yxe2x89xa61, 0xe2x89xa6zxe2x89xa61) in which the concentration of an n-type carrier is 1xc3x971019 cmxe2x88x923 or less, wherein the concentration of a p-type dopant is 1xc3x971017 cmxe2x88x923 or more and 1xc3x971021 cmxe2x88x923 or less, between the above-mentioned layer composed of the n-type III-V group compound semiconductor and a third layer composed of a p-type III-V group compound semiconductor represented by the general formula InaGabAlcN (a+b+c=1, 0xe2x89xa6axe2x89xa61, 0xe2x89xa6bxe2x89xa61, 0xe2x89xa6cxe2x89xa61), on the opposite side to the above-mentioned second layer.
Further, the present invention relates to [6] a method of producing a III-V group compound semiconductor according to any of [1] to [5], comprising growing a III-V group compound semiconductor represented by the general formula InxGayAlzN (x+y+z=1, 0xe2x89xa6xxe2x89xa61, 0xe2x89xa6yxe2x89xa61, 0xe2x89xa6zxe2x89xa61) in which the concentration of an n-type carrier is 1xc3x971019 cmxe2x88x923 or less, wherein the concentration of a p-type dopant is 1xc3x971017 cmxe2x88x923 or more and 1xc3x971021 cmxe2x88x923 or less, at temperatures of 600xc2x0 C. or more and 950xc2x0 C. or less according to a metal organic vapor phase growth method.
Further, the present invention relates to [7] a light emitting device obtained by using a III-V group compound semiconductor according to any of [1] to [5].